1. Field of the Invention
This invention relates to footwear apparatus and more particularly to that class utilizing sacks for fluidly supporting the user thereof.
2. Description of the Prior Art
The prior art abounds with devices adapted to provide an air cushion supporting the foot of the user attached to footwear. U.S. Pat. No. 2,981,010 issued on Apr. 25, 1961 to H. Aaskov teaches an air filled sandal having a plurality of compartments residing between the inner sole and outer sole. Each compartment communicates with the other compartments and is inflated by way of a valve communicating thereinto.
U.S. Pat. No. 3,120,712 issued on Feb. 11, 1964 to L. L. Menken discloses a sack disposed intermediate opposed surfaces of an insole and an outer sole. A rigid stiff member is affixed to the lowermost surface of the insole and rests upon the uppermost surface of the sack. The marginal edges of the stiff member approximate the innermost walls of the cavity in which the sack resides but are free from touching engagement therewith. Thus, the user's foot comes into contact with a substantially uniformly stiff member, freely floating upon the sack filled with a fluid.
The aforementioned patents suffer the common deficiency of providing a resting surface which, though cushioned by fluid pressure, is either uniformly stiff or uniformly responsive to changes in the level of pressure of the fluid utilized.